Homology model of the factor VIII C1 domain.

The homology model of the C1 domain (red) was created as described in the text and is superimposed onto the crystal structure of the factor VIII C2 domain (blue) and is shown in stereo views. The locations of the 19 β-strand structures in C2 are indicated,22referred to as β′ strands in C1. The major differences are in the loop lengths (Figure 1), which are indicated by gray arrows. The loop corresponding to the β3-β4 hairpin structure within the C2 domain, a putative membrane-binding surface, is shortened to a turn in C1 (thus, there is no β3′ or β4′ strand in C1; homologous numbering of strands 5′ through 19′ are preserved). The β5-to-β6 loop is 2 residues shorter in C1. The loop between β-strands 13 and 14 is 2 residues longer in C1.